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    Question

    a, b, c in GP; a + b + c = 21, abc = 216. Find

    numbers.
    A (3, 6, 12) Correct Answer Incorrect Answer
    B (3, 5, 11) Correct Answer Incorrect Answer
    C (1, 2, 12) Correct Answer Incorrect Answer
    D (3, 3, 9) Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let b = ar, c = ar² → a(1 + r + r²) = 21, a³r³ = 216 → ar = 6 → a = 6/r (1 + r + r²)/r = 3.5 → r² – 2.5r + 1 = 0 → r = 2 or 0.5 r = 2 → a = 3 → (3, 6, 12)

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